Alpha particle spectroscopy by automated analysis of etched alpha particle tracks in TASTRAK™ (CR-39) type plastic is described. The method is based on the measurement of two geometric parameters of etched tracks, the minor axis ( m), and the diameter of the etched out track end ( d). Accurate measurement of these two parameters allows reliable separation of tracks according to alpha particle energy, with a FWHM of 105–130 keV, or 1.5–2.5%, in an energy band of 1.5 MeV. Pre-etching the plastic at 98°C before exposure to the alpha particle source caused a decrease in V T/ V B, resulting in an improved energy resolution of 80–110 keV (1.33–2%), with a concomitant decrease in the energy band to 1.2 MeV. Within this band, the intrinsic measurement efficiency is as high as 0.75, a critical factor for possible low level measurement applications. The results indicate that a basis exists for a robust working method for alpha particle spectroscopy in TASTRAK™ plastic.